fix(block2): back buttons on social screens + clear 'Share my seeds' button

Two UX reports:
- Market/Messages (and Profile/Chat) had no back button — they were opened with
  context.go (replaces the stack). Switched the drawer entries, home Market card,
  offer 'Message' link and inbox taps to context.push, so the AppBar shows a back
  arrow to return.
- The market's upload icon (tooltip-only) was unclear. Replaced it with a labelled
  FloatingActionButton.extended 'Share my seeds' (campaign icon); the config gear
  stays in the AppBar.

Analyzer clean.

apps/app_seeds/lib/ui/app_drawer.dart

@@ -41,7 +41,7 @@ class AppDrawer extends StatelessWidget {
               onTap: marketEnabled
                   ? () {
                       Navigator.of(context).pop();
-                      context.go('/market');
+                      context.push('/market');
                     }
                   : null,
             ),
@@ -51,7 +51,7 @@ class AppDrawer extends StatelessWidget {
               onTap: marketEnabled
                   ? () {
                       Navigator.of(context).pop();
-                      context.go('/profile');
+                      context.push('/profile');
                     }
                   : null,
             ),
@@ -61,7 +61,7 @@ class AppDrawer extends StatelessWidget {
               onTap: marketEnabled
                   ? () {
                       Navigator.of(context).pop();
-                      context.go('/messages');
+                      context.push('/messages');
                     }
                   : null,
             ),